13/15 Archives of Foundry, Year 2005, Volume 5, № 15 Archiwum Odlewnictwa,

Rok 2005, Rocznik 5, Nr 15 PAN – Katowice PL ISSN 1642-5308

THE MICROSTRUCTURE OF THE SELECTED INOCULANTS

FOR USE CAST IRONS

E. GUZIK

1, M. PORĘBSKI

2, H. WOŻNICA

3, J. SZALA

4

1,2 AGH -University of Science and Technology, Reymonta 23St., 30-059 Kraków

3,4 Silesian University of Technology, Krasińskiego 8 St., 30-019 Katowice, Poland

SUMMARY

The type and composition of the phases present in KOMO (from

KOmpleksowy MOdyfikator - eng. Complex Inoculant) - a Polish inoculant and in

foreign inoculants (Foundrysil, SB-5, Ferrosilicon 75) have been investigated. The

purpose of those reactive elements is to combine with Ca, Al, Ba and Sr in the FeSi75

ferrosilicon and form potent heterogeneous nucleation sites for graphite. The structure

of the KOMO inoculant was proved to comprise silicon and an FeSi2 phase, as well as

two other phases containing Ba-Al-Sr-Si (with Ba prevailing) and Sr-Ca-Ba-Si (with Ca

and Sr prevailings). The combined effect of Ca, Al, Ba and Sr elements also give better

chill control than Ca +Al. The new KOMO inoculant is most effective in increasing the

nodule count in ductile cast iron, in grey cast iron with flake graphite, and in vermicular

cast iron. Finally conclusions are drawn, as related to the practical application of the

results obtained.

Key words: inoculation KOMO, cast iron, ductile iron, complex inoculant

1. INTRODUCTION

Graphitising inoculation is a very important and necessary step in the process of

making high-quality cast iron. Various types of inoculants are available at present, and

also in the domestic market numerous graphitising inoculants for molten cast iron are

offered by foreign, e.g. ELKEM (Norway), PECHINEY (France) SKW TROSTBERG

1 prof. dr hab. inż., email:guz@uci.agh.edu.pl 2 mgr. inż

3 prof. dr hab. inż., woznica@polsl.katowice.pl

4 prof. dr hab. inż., szalajan@polsl.katowice.pl

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(Germany), as well as domestic companies, e.g. Huta ŁAZISKA S.A. (Poland). The

trade names and chemical compositions of those inoculants are given in [1]; in Polish

foundries the inoculants compiled in Table 1 are in most frequent use. The inoculants

based on Fe-Si-Ca-Al alloy, containing also additions of barium and strontium, have not

been offered as yet. On the other hand, quite well known are the inoculants for cast iron

which, physically, constitute a mixture of ferrosilicon plus additives, like e.g. Fe-Si-Ca-

Al plus Ba (up to 20%) and Sr (2÷10%); they are protected by a Polish patent PL

130621 granted in 1986 [2]. Within the scope of the conducted research works aiming at

optimising the performance of inoculants for cast iron, and specially at reducing the

inoculant consumption rate and making its effect last longer, a batch of the Fe-Si-Ca-

Al-Ba-Sr inoculant containing 76 % Si; 0,49 % Ca; 1,1 % Al; 0,44 % Ba and 0,45 % Sr

was produced. The inoculant was melted at HUTA ŁAZISKA S.A. and was given

a trade name KOMO (from KOmpleksowy MOdyfikator - eng. Complex Inoculant).

Melting of the inoculant was described in [3]. The inoculant was subjected to tests

Table 1. Chemical composition of different inoculants for cast iron.

Tabela 1. Skład chemiczny różnych modyfikatorów dla żeliwa

No

.

Trade name of

inoculant

Chemical composition, wt %

Si Ca Al Ba other

1 Superseed 75 73 – 78 0,1 max 0,5 max - 0,6–1,0 Sr

2 Foundrysil 73 – 78 0,75–1,25 0,75 0,75-1,25 -

3 Zircinoc 73 – 78 2–2,5 1–1,5 - 1,3-1,8 Zr

4 Si 75A 73 – 78 2–5 1–1,5 - -

5 SB5 64 – 70 1 1,5 2 -

6 SMW 605 60 – 64 1,8 – 2,4 0,8 max - 1 RE, 1 Bi

7 SRF 75 73 – 76 0,1 max 0,5 max - 0,6–0,9 Sr

8 ZL 80 74 – 76 2,5 1,4 - 1,5 Zr

9 Superssed 50 45-50 0,1max 0,5max - 0,6-1,0Sr

10 Barinoc 73-78 1-2 0,8-1,5 2-3 -

11 Inobar 64 1 1,3 9 -

12 LMC 66 1,7 0,8 0,8 -

13 SZR504 45-50 2,5-3,5 1 - Zr

14 SiCa 60-65 30-33 1,5max - -

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conducted under both laboratory and industrial conditions to examine its effectiveness

in the process of manufacturing high-quality cast iron. The aim of the present study was to determine the type of microstructure and the

composition of phases present in inoculants of the KOMO type and in some selected

imported inoculants containing calcium, aluminium, or - additionally - barium, affecting

the number of graphite nuclei formed in cast iron.

2. RESULTS AND THEIR ANALYSIS

The results of the examinations of the number of eutectic grains falling to a unit

surface and of testing some selected mechanical properties, i.e. tensile strength UTS,

elongation A and hardness HB, obtained in inoculated, ductile and vermicular cast irons

using KOMO inoculant were described in [3,4]. The industrial trials confirmed the high

effectiveness and versatile effect of this inoculant when applied to the three mentioned

above cast irons, this additionally matched with its high profitability.

The high useful value of the KOMO-type inoculants, well proved in cast iron in

comparison with e.g. an FeSiCaAl (Si75A) inoculant and an inoculant additionally

containing barium (SB-5 and Foundrysil - see Table 1), is without any doubt caused by

a different morphology and chemical composition of phases present in their structure.

Fig. 1. The distribution of the Si, Al, Sr and Ba elements in a KOMO- a Polish type inoculant.

Rys. 1. Rozkład Si, Al, Sr i Ba w polskim modyfikatorze KOMO

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Point 1 Point 2

Element at. % wt % element at.% wt %

Si 69,69 45,48 Si 58,25 43,18

Ca 1,36 1,27 Ca 32,26 34,13

Ba 12,65 40,38 Ba 0,58 2,10

Sr 1,88 3,83 Sr 8,90 20,59

Al. 14,42 9,04 Phase: Sr - Ca - Ba - Si

Phase: Ba - Al - Sr - Si

Point 3 Point 4

Element at. % wt % element at.% wt %

Si 68,17 52,39 Si 100 100

Fe 30,07 45,96 Phase: Si

Al. 1,30 0,97

Mn 0,46 0,69

Phase: Fe Si2 Fig. 2. The distribution and chemical composition of phases occur in a KOMO inoculant.

Rys. 2. Rozkład i skład chemiczny faz występujących w polskim modyfikatorze KOMO

The examinations revealing these differences were conducted on a Hitachi S-4200

scanning microscope equipped with an X-ray detector. Due to the use of the detector it

was possible to enlarge the scope of application of this device and perform qualitative

as well as quantitative analysis of the chemical composition in microregions. The results

of these examinations, supported by a mapping technique [5], enabled revealing the

specimen regions of a typical phase constitution. Examples of the images of

microstructures and the distribution of the elements Si, Al, Sr, Ba presents in KOMO,

inoculant are shown in Figures 1 and 2.

The binary images of the regions with determined mass fraction of the selected

elements were obtained by means of multiple binarisation [5]. Using these images, the

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distribution maps of the most important phases present in the examined inoculants were

drawn. The structure of the KOMO inoculant was proved to comprise silicon and an

FeSi2 phase, as well as two other phases containing Ba-Al-Sr-Si (with Ba prevailing)

and Sr-Ca-Ba-Si (with Ca and Sr prevailings). Without any doubt these two phases

present in the structure of the inoculant while it is added to cast iron are responsible for

the formation of a large number of the nucleation sites for nodular or flake graphite in

high-quality cast iron, ultimately expressed by a large number of the eutectic grains.

KOMO - Poland

Huta Łaziska S.A.

SB- 5 or Foundrysil

SKW Trostberg -

Germany

FeSi75

ELKEM - Norway

Fig. 3. The distribution of the main phases present in inoculants: KOMO - (FeSi+Ca+Al+Ba+Sr),

and SB-5 or Foundrysil - (FeSi+Ca+Al+Ba) as well as in Ferrosilicon – ( FeSi+Ca+A)l. Rys. 3. Rozkład głównych faz występujących w modyfikatorze KOMO – (FeSi+Ca+Al+Ba+Sr),

i SB-5 lub Foundrysil – (FeSi+Ca+Al+Ba) a także w Ferrosilicon – ( FeSi+Ca+A)l.

This can explain the high inoculation power of this agent, compared with the

ferrosilicon-type inoculants, which contain Ca and Al only, possibly also barium

(Figure 3). In an FeSi+Ca+Al inoculant (the trade name according to Polish Standard –

Si75A), besides the precipitates of Si and FeSi2 phase, two other phases containing Al-

Ca-Si and Ca-Si were detected, while in a barium-containing inoculant the first phase

was additionally enriched with barium. The phases of this inoculant act as sites for

graphite nucleation in cast iron, but they are much less effective than the phases

composed of Ba-Al-Sr-Si and Sr-Ca-Ba-Si present in new domestic inoculant of the

KOMO-a Polish type.

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REFERENCES

[1] Guzik E.: Some selected problems concerning the processes of cast iron

improvement, Archives of Foundry, Polish Academy of Sciences - Branch

Katowice, A Monograph No. 1M, XI, 2001, pages 128.

[2] Pietrowski S. et al.: Graphitising inoculation for cast iron, Polish Patent PL

130621 of 02.12.1986.

[3] Guzik E., Porębski M.: A new complex inoculant for high quality cast iron, Acta

Metallurgica Slovaca, Vol. 2, (2002), pp. 10-15.

[4] Dudzik B., E. Guzik.: Massive high quality castings made of vermicular cast

iron, XXX School of Materials and Engineering, Kraków – Ustroń -Jaszowiec,

1-4.Oct., (2002), pp.227-232.

[5] Szala J.: Application of computer - aided image analysis methods for a

quantitative evaluation of material structure, Archives of Metallurgy,

Monograph No. 61, Silesian University of Technology, Gliwice, 2001, pages

167.

MIKROSTRUKTURA WYBRANYCH MODYFIKATORÓW

PRZEZNACZONYCH DLA ŻELIWA

STRESZCZENIE

W opracowaniu przedstawiono mikrostrukturę krajowego modyfikatora typu

KOMO oraz modyfikatorów importowanych typu: żelazokrzemu FeSi (zawierającego

Al i Ca), Foundrysil oraz SB-5 (zawierających Al, Ca i Ba) przeznaczonych dla żeliwa

wysokojakościowego: modyfikowanego, sferoidalnego i żeliwa z grafitem

wermikularnym. Wskazano na istotną różnicę w budowie faz występujących w tych

modyfikatorach; w strukturze modyfikatora KOMO występują następujące fazy Ba-Al-

Sr-Si, Sr-Ca-Ba-Si, FeSi2 oraz krzem, natomiast w modyfikatorach importowanych

dwie pierwsze fazy pozbawione są takich kombinacji ilościowych pierwiastków jak Ba

i Sr. Wyjaśniono, dlaczego walory modyfikujące krajowego modyfikatora typu KOMO

produkcji Huty ŁAZISKA S.A. są lepsze od modyfikatorów importowanych.

Recenzował Prof. Jan Szajnar